LECTURE 10
Announcements
Final 1 Feedback
• Almost completely done with your
2D game engine!
– Congratulations!
– Feel free to use it/improve after
the class is over (some of us
have/still are)
• Time to start showing off your
product
– ~2.5 weeks of gameplay coding!
– Content creation!
– Tons of playtesting!
• More on public playtesting later…
Hours change?
• For specific problems you
should be talking to your
mentor TA
• We’ll hold hours for issues
with finishing up late
projects
– What times work best?
• Will announce times after
grading meeting today
Special topics AI lecture!
• It’s the week after
thanksgiving
• It’ll be great
Next Week Doesn’t Exist
• No lecture
• No hours
• No assignment due
• Final II due the next week
• Doesn’t count against retries
• Final I retries due the next
week
Deadline Approaching
• Course policy: you must turn in a working version of
all projects
• Deadline for incomplete projects is December 20
• Same day as Final V
• Make sure to email the TA staff when you re-turn in!
Announcements
QUESTIONS?
LECTURE 10
Sound
Sound
SOUND APPLICATIONS
Sound in Games
• In the real world,
computers have sound
• Background music
• Sound effects
• Can be an important part
of gameplay
– Listening for footsteps
– Dramatic music
Sound File Formats
• Many ways to encode and
store sound
• Open standards
– Ogg Vorbis
– FLAC
• Closed standards
– mp3
– m4a
– wav
Sampled Audio
• mp3, wav, and most other
familiar extensions
• Usually recordings of live
sounds
• Samples of sound wave at
regular intervals
• Prevalent in modern games
• Refers to data type, not
origin
– Touchtone telephone is
generated but still sampled
1100100110101011011101011001000110101
Generated Audio
• MIDI
• File provides information on
instruments and notes
– Similar to sheet music
• Sound cards translate from
instruments/notes to sound
• Can instruct computer to play
something even if you can’t
play it
• Used to be popular to save
space, not as common now
Compressed vs. Uncompressed
Compressed Sound Files
• Lossy or Lossless?
– Lossy remove “least important”
parts of sound wave
– Lossless just use smart
compression on raw wave
•
•
•
•
Smaller file size (esp. lossy)
Lossy is lower quality
Slower to decode and play
Often used for music
Uncompressed Sound Files
• Record as much as
possible of sound wave
• Much larger file size
• Usually high quality
• Faster to decode and
play
• Often used for sound effects
Buffering
• Decompressing and
decoding is slow
• Read sound into buffer,
play back from buffer
• Size of buffer depends on
speed of system
• Playback delay while
buffer is filled
Sound
device
Buffer
Decoding
Sound file
Sound
SOUND IMPLEMENTATION
javax.sound.sampled
•
•
•
•
•
AudioSystem: Provides factory
methods for loading audio sources
Clip: Any audio that can be loaded
prior to playback
Line: Any source of streaming audio
DataLine: An implementation of Line
with helpful media functionality (start,
stop, drain, etc)
Other classes for mixing, ports, and
other utilities
File file = new File(“mysound.wav”);
InputStream in =
new BufferedInputStream(
new FileInputStream(myFile)
);
AudioInputStream stream = AudioSystem
.getAudioInputStream(in);
Clip clip = AudioSystem.getClip();
clip.open(stream);
clip.start();
javax.sound.midi
• MidiSystem: The
AudioSystem for MIDI files
• Sequencer: Plays MIDI sounds
• Other classes for manipulation
of instruments, notes, and
soundbanks
– So you can create MIDI sounds
in realtime
– Much harder to manipulate
samples
Sequence song =
MidiSystem.getSequence(new
File(“mysong.midi”));
Sequencer midiPlayer =
MidiSystem.getSequencer();
midiPlayer.open();
midiPlayer.setSequence(song);
midiPlayer.setLoopCount(0);
midiPlayer.start();
Alternatives?
• Some drawbacks of the built-in
sound classes…
– Imprecise control over exact
playback start/stop positions
– Almost impossible to manipulate
or even examine samples in
realtime
– While Java offers pan and
reverb, other libraries offer
more varied effects
• But it’s very effective for simple
background music and sfx!
OpenAL
• Cross-platform audio API
modeled after OpenGL
• Pros:
– Built for positional sound
(distance attenuation, Doppler
shift, etc all built in)
– More fine-grain control
available
• Cons:
– Single listener model
– Modeled on OpenGL
Others
• Most other libraries are
platform-specific or
wrappers for OpenAL
• …except for synthesis
libraries!
– Jsyn, Beads, etc
– Useful for composer
programs and the like, not
so much for sound playback
Sound
QUESTIONS?
LECTURE 10
Data Persistence
What to Save?
• Settings
– User profile
– Game settings
• Game state
– Progress through the
game
– Maybe the state of the
world or current level
Where to Save?
• Data should be saved somewhere that is
always accessible by your program!
– Oftentimes the user’s home directory can be used
for this purpose
• Saving data to the current directory will not
work, as your program can be run from
anywhere!
Data Persistence
PERSISTENT CONFIGURATION
User Settings
• Player name
• Custom controls
• Other In-game
preferences
• Considerations
– Need to save per user
– Should be able to export
between game instances
– Ideally put in cloud sync
Saving Game Settings
• Preferred resolution
• Graphics detail level
• Input source (keyboard,
peripheral, etc)
• Considerations
– Need to save per
installation of game
– Should not go in cloud
storage – machine-specific,
can’t “sync”
Strategies
• Serialize a Java object
• Java properties file
• XML/JSON file
– Easy for humans to read
– Harder to parse
• Custom text format
– Can be more concise, easy
to parse
User Interface
• User probably doesn’t
need to know file
location
– Still make it easy to find
so user can back it up
• Don’t save automatically,
revert graphics changes
if no response
Data Persistence
SAVING GAME STATE
When to Save Game
• Only at checkpoints
– Easier to implement
– Each checkpoint is a level,
reload level when player
dies
– Potentially more frustrating
for player
– Ensure they’re frequent
enough
When to Save Game
• Any time at save stations
– Like checkpoints, but user
can go back and resave
– Better for nonlinear
games
– Need to save level state/
progress, but not exact
positions (save room
usually empty)
When to Save Game
• Whenever user wants
– Harder to implement,
need a “snapshot” of
current game state
– Good for difficult games
with frequent failure
– Can still restrict when
user can save (e.g. not
during combat)
Automatic Saving
• A good idea if the player is
responsible for saving
– Just because saves are
available doesn’t mean user
will use them
• Don’t set user too far back
when they fail
• Depending on
implementation, can simplify
saved state (ie, only save
when no enemies are
around)
User Interface
• Save slots
– Easy, simple, annoying
• Native file browser
– Easy way to allow
arbitrary saves
– Doesn’t mesh well with
game, unprofessional
User Interface
• Custom save-file browser
– Harder to implement, but
most flexible/featureful
• Features
– Screenshot of saved game
– Show only current player’s
saves
– Sort by time & type of save
Strategies
• Save serialized copy of game world
– On restore, use serialized data as the world
• Save information about which level the player is on and
where entities are located
– On restore, load the level fresh and then apply changes
• Save some concise file with relevant state information
– On restore, act accordingly… like warp to nearest
checkpoint, or load the level and place player at save point
Gotchas
• Serializing the world…
– Whoops! We just serialized input
states, the screen stack, player
preferences…
– Solution: correctly label with
Serializable
• Saving generated levels…
– Can’t just store level file name!
– Solution: Either save the seed and a
list of changes, or convert
generated map into some savable
format
• The same error-handling warnings
from Tac apply
Data Persistence
QUESTIONS?
LECTURE 10
Procedural Content II
Procedural Content
CLASSIFICATION
What is procedural content?
• Procedural content: game
content generated in an
algorithmic way rather
than by a designer
• Procedural content
generation: the generation
of this content via a semirandom process
Generated Content
• “Procedural generation” in
common usage usually
refers to any randomized
aspect of game content
• All procedural content
need not be generated, or
generated randomly
– Content deterministically
inferred from other content
Why use procedural content?
• Historically: memory
restrictions required it
• Generating by hand is
tedious and/or expensive
• In the case of procedurally
generated content, provide
a new experience with every
game
• Provide a personalized
experience
Online vs. Offline
• Online
– Game content is generated
on the fly
– Limitless potential!
• Offline
– Game content is generated
by algorithm and then
packaged with the game
– Can be perfected by a
human designer
Necessary vs. Optional
• Necessary
– Required by the player to
progress in the game
– Must always be correct or
useable
• Optional
– Player can choose to avoid
or bypass
– Some weirdness is fine
Random vs. Parameterized
• All procedural content
performs some sort of
expansion from compressed
data to real content
– What is the compressed form?
• Random
– Compressed form is RNG seed
• Parameterized
– Compressed form is a
parameter vector
– Most often used for
personalized content
Constructive vs. Verified
• Constructive
– Generate the content and
be done with it
– Need to make sure it’s
correct at every step
• Verified
– Both a content generator
and a content verifier
– Generate the content until
it’s suitably fit
Procedural Content
QUESTIONS?
Classification quiz!
Classification quiz!
Procedural Content
APPLICATIONS
Procedural Animation
• Animating every pose of a
character can be difficult
• Generate poses by joints
and constraints
• Can even animate each
portion separately
• Could also refer to
particle effects
Dynamic Lightmaps
• Lightmaps are used to
store lighting information
– Separate from textures
– Provides significant
graphical speedup
• Rather than defining them
for each object, generate
them algorithmically
Natural Textures and Terrain
• Perlin noise: generated
visual effect that simulates
natural texture
• Even used in CGI for
flames, smoke, clouds etc
• Computed by calculating
distance to grid vertices
then interpolating
Level Generation
• Create random level layouts
at runtime
• Can be used to make
dungeons, interiors, cities,
maps, etc
• Algorithms are numerous and
vary by purpose
– Popular dungeon algorithm:
subdivide dungeon in a binary
tree, add a room to each
Design of Level Content
• Generate many enemies or
weapons with different
attributes, then pick those
that most satisfy the scenario
• Alternatively, generate many
levels then evaluate them via
a fitness function
• Underpins most sandbox
games
Dynamic World Generation
• Entire game world is
generated on the fly
• No part of the world is
written to disk
– Unneeded parts are
immediately disposed
• Hinges on deterministic
generation and a single
RNG seed
• Used in EVE Online as well
as a variety of older games
Instancing In-Game Entities
• Each entity has some
value randomized
– All entities are similar,
but have some
distinguishing feature
• Usually used to create
names, faces, item or
weapon properties
Dynamic Systems
• Model complex behaviors
with simple sets of rules
• Used for weather, crowds,
spreading fire, and other
bottom-up effects
• Strong ties to certain
areas of AI, like swarm
intelligence
Plot and Puzzle Generation
• Think of a game’s storyline as
a dependency graph
• Graph dependencies can be
changed
– For example, move a key to a
random accessible location
• Graph structure can be
changed
– Alters order of events
• Can also use natural language
processing to create characters
and stories
Procedural Content
QUESTIONS?
LECTURE 10
Tips for Final 2
Tips for Final 2
EFFECTIVE PLAYTESTING
Finding Playtesters
• CS students are easy
targets, try the sun lab or
MS lab
– Ask nicely
– Don’t ask busy people
• Keep your audience in
mind, however
– It probably isn’t all CS
students
Don’t Interrupt!
• Be a fly on the wall
– Say as little as possible
– Don’t offer hints or
instructions
• Your game should
speak for itself
– You won’t be there to
offer instructions when
your game is released
When to Interrupt
• Player is frustrated or
taking too long in a
single area
• You’re no longer getting
good feedback
• If the player moves on,
you will resume getting
good feedback
Keep a Log
• What is the player getting
stuck on?
– Make it smoother
• What is the player enjoying?
– Emphasize it
• What is the player ignoring?
– Take it out if it’s unnecessary
• Consider having the game
keep an automated log
– Analytics is wonderful!
Tips for Final 2
QUESTIONS?
Tips for Final 2
JAVA TIP OF THE WEEK
Default Visibility
• You already know public,
private, protected
• What happens when
there’s no visibility
modifier?
• Then the field/method is
visible to anything in the
same package
A Helpful Table
Own Class
Same
Package
Subclass
All Others
public
Visible
Visible
Visible
Visible
protected
Visible
Visible
Visible
No
(default)
Visible
Visible
No
No
private
Visible
No
No
No
Some General Visibility Tips
• Use private wherever
possible
– “Encapsulation”
• If you have a large
amount of protected
methods you want truly
protected, consider
separating them into an
interface
Tips for Final 2
QUESTIONS?
NO PLAYTESTING?
Playtest with random people
this week!